Intelligent Power Management System and Method for Monitoring Battery Integrity

The present application claims the benefit of priority to U.S. Provisional Application No. 63/658,673 filed on Jun. 11, 2024, which is hereby incorporated by reference in its entirety for all purposes.

The present disclosure relates to electrical circuit topologies and control methods for monitoring the structural integrity of batteries. Electric vehicles, standby power supplies, power stations, and other mobile and stationary battery electric systems utilize rechargeable batteries as energy storage devices. The rechargeability and high energy storage capacities of lithium-ion batteries in particular has led to widespread adoption of such batteries in a myriad of industries. For example, lithium-ion batteries are used to power electric motors in mobile and stationary battery electric systems, as well as to energize actuators, sensors, displays, and control circuits of medical devices, industrial systems, and consumer products.

While lithium-ion batteries are integral components of battery electric systems, their use comes with certain potential risks. For instance, the internal temperature of an aged or faulty battery cell can rapidly increase. Thermal management techniques such as coolant/air circulation or the use of heat sinks or cell vents are therefore used to help regulate battery temperature. However, when the temperature of a given battery cell increases beyond a point, the materials of the battery and its constituent cells can begin to melt or burn. The resulting pressure increase within the battery cell can cause the cell can or outer foil to rupture. When this happens, the cell expels high-temperature gasses, molten materials, soot, and other ejecta, which can propagate to neighboring battery cells. This condition is referred to in the art as thermal runaway, and can adversely affect operation of the battery and battery electric system as a whole.

Disclosed herein are battery monitoring systems and automated methods for monitoring a rechargeable lithium-ion or other rechargeable battery of a battery electric system. The present teachings seek to protect the battery electric system and surrounding surfaces or components from thermal damage by detecting a potentially hazardous degradation state of the battery prior to manifestation of the hazard. The present teachings thus enable issuance of an alert as an advanced warning of an impending battery failure, which in turn provides operators with sufficient time with which to perform preventive actions such as battery replacement or circuit disconnection.

The monitoring strategy as contemplated herein determines an internal resistance of the battery during two states: (1) a charging mode during which the battery is actively receiving a charging current, with the internal resistance during such a charging mode referred to below as the “charge-side resistance”, and (2) a discharging mode during which the battery provides a battery current to a connected load, with the internal resistance of the battery during such a discharging mode referred to as the “discharge-side resistance”. The two internal resistance values are then used to evaluate the present state of health (SOH) of the battery.

Above a predetermined threshold indicative of a potentially hazardous state of the battery, one or more preventive control actions may be performed to help avoid thermal damage to the battery and/or the battery electric system and its surrounding environment.

According to a representative embodiment, a battery monitoring system (BMS) includes a sensor array connectable to a battery, a processor, and a non-transitory computer-readable storage medium (“memory”). The memory includes instructions executable by the processor to cause the processor to calculate a charge-side resistance (R) and a discharge-side resistance (R) of the battery during the charging and discharging modes, respectively. The processor receives a voltage, a current, and a temperature of the battery from the sensor array during a charging mode of the battery and during a discharging mode of the battery. A degradation level of the battery is calculated using the charge-side resistance (R) and the discharge-side resistance (R). A preventive action of the battery is optionally performed in response to the degradation level exceeding a calibrated threshold.

Also disclosed herein is a method for monitoring a battery in a battery electric system. An embodiment of the method includes calculating a charge-side resistance (R) of the battery via the EMU during the charging mode using, calculating a discharge-side resistance (R) of the battery via the EMU during the discharging mode, and then calculating a degradation level of the battery using the charge-side resistance (R) and the discharge-side resistance (R). A preventive action of the battery may also be performed in response to the degradation level exceeding a calibrated threshold.

A battery electric system is also disclosed herein. An embodiment of such a system includes a battery connectable to a battery charger during a charging mode, a load connectable to the battery and energized thereby during a discharging mode, a sensor array connected to the battery, and an electronic monitoring unit (EMU). The EMU is configured to transmit a measurement request signal to the sensor array, and to receive, in response to the measurement request signal, first and second sets of battery parameters from the sensor array during the charging and discharging modes. The battery parameters include at least a voltage, a current, and a temperature of the battery.

The EMU in this implementation is configured to calculate a charge-side resistance (R) of the battery during the charging mode using the first set of battery parameters, a discharge-side resistance (R) of the battery during the discharging mode using the second set of battery parameters, and a degradation level of the battery using the charge-side resistance (R) and the discharge-side resistance (R). Thereafter, the EMU performs a preventive action of the battery in response to the degradation level exceeding a calibrated threshold.

The above summary is not intended to represent every embodiment or aspect of the present disclosure. Rather, the foregoing summary exemplifies certain novel aspects and features as set forth herein. The above noted and other features and advantages of the present disclosure will be readily apparent from the following detailed description of representative embodiments and modes for carrying out the present disclosure when taken in connection with the accompanying drawings and the appended claims.

The present disclosure may be modified or embodied in alternative forms, with representative embodiments shown in the drawings and described in detail below. Inventive aspects of the present disclosure are not limited to the disclosed embodiments. Rather, the present disclosure is intended to cover alternatives falling within the scope of the disclosure as defined by the appended claims.

With reference to the drawings, wherein like reference numbers refer to the same or similar components throughout the several views, a battery electric systemis illustrated schematically in. The battery electric systemin a simplified embodiment includes a rechargeable battery, an electrical switch, a load (L), and a battery monitoring system (BMS). The BMSin turn includes a sensor arrayand an electronic monitoring unit (EMU), with the sensor arraybeing connectable to the battery, for instance via hard-wired transfer conductors and/or wireless connections.

The EMUas contemplated herein includes a processor (P)and a non-transitory computer-readable storage medium (“memory”) (M). The memoryincludes instructions recorded thereon and executable by the processorto cause the EMUto perform a method, a non-limiting example of which is described below with reference to. Among other actions, the EMUtransmits a measurement request signal (CCR) to the sensory arrayof the BMSto initiate the present process.

The batteryofis described hereinafter as a lithium-ion (Li) for illustrative consistency, but may be alternatively configured as another rechargeable battery in other embodiments, for instance as a lithium metal oxide (LMO), lithium metal, nickel-metal hydride (NiMH), nickel-cadmium (NiCd), or another application-specific battery chemistry. In various implementations, the battery electric systemcan be used as part of a mobile or stationary battery-powered device. For instance as shown in, the batterymay be used to power a portable electronic device such as a computerA, e.g., a tablet, desktop, or laptop computer, or a cellular phoneB.

Other applications may use the batteryas part of a medical device, for instance a handheld surgical toolC, or a wearable deviceD such as a continuous glucose monitor (CGM) as shown, or alternatively an automatic external defibrillator (AED), blood oxygen monitor, or infusion pump. Likewise, the batterymay be used to energize a mobile systemE such as an electric vehicle. Still other applications may be readily envisioned, including but not limited to electronic gaming systems, control consoles, or other industrial, medical, or transportation systems. The exemplary use, chemistry, construction, and simplified depiction of the batteryherein is therefore illustrative of the present teachings and non-limiting thereof unless otherwise specified.

The BMSofmay include other components in different embodiments. For example, a direct current-to-direct current (DC-DC) convertermay be used with the batteryto increase or reduce the battery voltage before energizing the load. A battery chargermay be connectable to the batteryto recharge the batteryas needed. In an alternating current (AC) configuration of the battery electric system, the batterymay be connected to a DC-to-AC inverter circuit, with the inverter circuitoperable for outputting an AC waveform to a coupled load (L). The loadsandmay be variously embodied as electric motors, rotary actuators, linear actuators, displays, transducers, and/or other electrical or electromechanical devices depending on the application.

As part of the present strategy, various sensors S, S, . . . , SN of the sensor arrayare used to measure or sense battery parameters during charging and discharging modes of the battery. The battery parameters used as part of the method() include at least a voltage, a current, and a temperature of the battery, with the EMUalso being configured to determine the state of charge (SOC) and an open-circuit voltage (OCV) of the batteryand its present charge/discharge state.

As part of the contemplated approach, input signals (CC) from the sensor arrayare communicated to the EMU. The EMUthereafter outputs electronic control signals (CC) to a remote device, e.g., a graphical user interface (GUI) as shown, a display screen, and/or to the disconnect switch. The disconnect switchmay be embodied as electromechanical contactors or relays, e.g., solid state relays (SSRs), operable to disconnect the batteryunder certain fault conditions. Although omitted fromfor illustrative simplicity and clarity, the battery electric systemmay be equipped with a thermal management system as summarized above to help regulate temperature of the batteryduring its normal operation, for example cooling plates, fins, heat sinks, coolant conduit, etc. Likewise, other circuit components such as fuses may be implemented to ensure the safety and reliability of the battery electric systemduring its operation.

Referring now to, which collectively illustrate the batteryofat various levels of charge depletion, the present teachings proceed with an understanding that the internal resistance of the representative batterywill tend to increase over time due to age-related and other degradation.depicts a new/properly functioning batteryhaving a useable nominal usable capacityof 100% and an internal resistance (R). Progressive aging and deterioration of the batteryis illustrated infor usable capacitiesof 75% and 50%, respectively. Relative to the new state of the batteryin, the internal resistance of the batteryinhas increased, in this exemplary instance to (4/3)R. As age-related degradation continues, the internal resistance (R) may continue to increase, in this exemplary case to twice the level of, i.e., 2R. In other words, age-related degradation of the batteryleads to a significant increase its internal resistance.

Referring briefly to, a bifurcated modelis used herein as part of the present strategy. That is, the internal resistance (R) of the batterydescribed above with reference tois divided herein into two respective components: (1) a charge-side resistance (R), and (2) a discharge-side resistance R. As noted above, Rand Rrespectively represent the internal resistance of the batteryas determined during charging and discharging modes of the battery. As shown in, the charge-side and discharge-side resistances are equal for a new/properly functioning battery, i.e., R=R. The rate of increase in the internal resistance is also approximately the same for the respective charge-side and discharge-side internal resistances Rand Ras the batteryages under normal usage conditions.

As shown in, however, this “lock-step” relationship between Rand Rchanges for a damaged battery such that the charge-side resistance (R) exceeds the discharge-side resistance (R), i.e., R>R. An ever-widening difference emerges between respective charge-side and discharge-side resistances Rand Ras the batterycontinues to degrade towards a potentially hazardous state. This degradation trajectory is closely monitored by the BMSofas described herein, which enables the BMSand its resident EMUto proactively take preventive measures when protecting the battery, the battery electric system, and the surrounding environment from potential thermal damage.

Rand R2: During a battery charging operation of a representative lithium-ion configuration of the battery, lithium ions migrate within the batteryand are absorbed onto electrode surfaces in a stable manner. However, abnormal growth and formation of unstable lithium deposits can result from repeated charging cycles or increased charging rates, e.g., during direct current fast-charging of the battery. Clusters of deposits can form elongated branch-like structures called dendrites. Dendrites and other lithium accumulations increase the charge-side resistance.

Dendrite formation in a lithium-ion battery cells is more pronounced relative to similar accumulations during discharge. While the discharge process also increases internal resistance, the accumulation of lithium deposits on the electrode surfaces during discharge modes tends to be less abnormal. The rate of increase in the discharge-side resistance (R) is therefore lower than the increase rate of the charge-side resistance (R). Thus, the absolute difference between the values Rand R, and/or their respective rates of change are monitored and tracked by the EMUofto ascertain the state of health (SOH) of the batteryand, if needed, take one or more protective or preventive actions to protect the batteryand/or the battery electric systemfrom thermal damage.

Referring to, the battery electric systemis illustrated schematically as the BMSand the load. During a charging mode, the batteryis disconnected from the loadvia the disconnect switches. A charging switch (SW)is commanded to close, e.g., by the EMUor another charging controller, which connects the batteryto the battery charger. As appreciated in the art, the battery chargermay be connected to an offboard power supply (not shown). When the power supply is an AC outlet, the battery chargerincludes an AC-to-DC converter to convert, filter, and output suitable DC voltage and current waveforms to the batteryfor charging. A current sensor (S), which is part of the sensor arrayofdescribed above, may be used to detect the current flow direction and therefore help determine whether the batteryis in a charging mode or a discharging mode. The batteryis removed from the battery chargerwhen the batteryis in use (discharging mode), with removal of the batteryfrom the battery chargerautomatically opening the charging switch.

In a possible implementation of the EMU, corresponding hardware and software modules or blocks may be implemented to perform the requisite processing functions of the method(). A state of charge (SOC) blockmay be used to determine the present SOC of the battery. The SOC blockmay be implemented in various ways, such as but not limited to Coulomb counting. In such an approach, current flowing into and out of the batteryover time is tracked and integrated to determine the amount of transferred charge. Other approaches may include, e.g., machine learning, voltage and temperature-based lookup tables, temperature-specific OCV-SOC tables or curves, or other possible approaches.

The EMUmay also include a voltage measurement block. This feature may be implemented using a voltage sensor Sof the sensor array(), with the measured voltage periodically measured and communicated to the voltage measurement blockand stored in non-volatile portions of the memory. An internal resistance calculation blockmay be used to calculate the charge-side resistance Rand the discharge-side resistance Ras part of the methodofusing data from blocksandas described below, along with measured current values from a current measurement block. The current sensor (S) likewise measured and communicates a measured current value (IDD) to the internal resistance calculation block, and to a charge/discharge detection blockto determine when the batteryis charging or discharging. As noted above, this may be accomplished by detecting the current flow direction through the batterywhich, due to the presence of diodes Dand D, may ordinarily in a single direction when the diodes Dand Dare properly configured and properly functioning.

The EMUalso considered battery temperature in evaluating the SOH of the battery. To that end, the EMUis equipped with a temperature measurement blockwhich is in communication with a temperature sensor S, e.g., a thermistor or thermocouple. The measured battery temperature (T) may be requested by, communicated to, and recorded by the temperature measurement block, possibly with assistance of an analog to digital converter (ADC). The measured battery temperature (T) is then communicated to a battery state blockoperable for determining an aging status of the battery, specifically its level of degradation. This function is performed using the reported charge-side and discharge-side resistances Rand R.

When the charge-side and discharge-side resistances Rand Rare high relative to thresholds as described below, alerts may be communicated by the EMUvia the output signals (CC), for instance to the GUIor another external audio and/or visual device. Depending on the application, the alerts may entail audible alarms, indicator lights, text messages, or the like, which may include a request to discard or replace the battery. When the EMUdetermines that failure of the batteryis imminent, the EMUmay take other preventive measures such as disconnecting the loador preventing charging via the battery charger. Such actions may help prevent thermal damage to the surrounding environment or, for wearable versions of the battery electric system, to a user of the wearable device.

Relevant parameters of the batteryusable as part of the methodofare explained with reference to.is a voltage plotof battery voltage in millivolts (mV) versus the remaining capacity of the battery, with the remaining capacity expressed as an SOC percentage (%). Tracesandrepresent the battery voltage during a charge mode and discharge mode of the battery, respectively, for a given temperature. Movement between tracesandthus represents a voltage difference (ΔV) relative to a baseline, i.e., the open-circuit voltage (OCV). For a given temperature and capacity, therefore, the OCV acts as a stable reference from which the voltage difference (ΔV) may be determined as part of method. As appreciated in the art, the OCV, e.g., from a temperature-specific lookup table referenced or indexed by SOC and OCV, may be used to determine the voltage difference (ΔV) as shown. That is, ΔV is the difference in a measured battery voltage and the OCV, i.e., ΔV=Δ−OCV.

illustrates via tracesthat the internal resistance of the batteryincreases in conjunction with state of charge (SOC) of the battery. This resistance, represented in ohms (Ω), is temperature-specific. For instance, tracerepresents the resistance-to-SOC relationship for a representative batteryat −10°° C. Similarly, traces,,, andrepresent the resistance-to-SOC relationship at 0° C.,10° C.,25° C., and60° C., respectively. The batteryat its lowest temperature in this example range therefore has the highest internal resistance at a given SOC. Thus, the present teachings may rely on one or more temperature-specific lookup tables including the SOC and OCV of the batteryas part of the operation of the EMU.

Referring now to, the methodis described as a sequence of steps or logic blocks, each of which may be embodied as computer-readable instructions. Such instructions may be recorded in memoryof the EMUof, or in another accessible non-volatile, non-transitory memory location, and executed by the processorto cause the EMUto perform the described functions.

With brief reference to, execution of the instructions embodying the methodofinvolves the cooperative use of the processor, the memory, and the sensor arraywhen evaluating the SOH of the battery. The functions of methoddescribed in detail below are embodied computer-readable instructions and executed from the memory, for instance magnetic or optical media, CD-ROM, and/or solid-state/semiconductor memory (e.g., various types of RAM or ROM). The processormay encompass one or more control modules, control units, microprocessor chips, Application Specific Integrated Circuit(s) (ASIC), Field-Programmable Gate Array(s) (FPGA(s)), electronic circuit(s), or central processing units. Associated memory component(s) of the memoryinclude non-transitory computer-readable storage devices such as read only memory, programmable read only memory, hard drive, etc. Non-transitory components of the memoryused herein are capable of storing machine-readable instructions in the form of one or more software or firmware programs or routines, combinational logic circuit(s), input/output circuit(s) and devices, signal conditioning and buffer circuitry and other components that can be accessed by one or more of the processorsto provide a described functionality.

In general, execution of such instructions from the memoryleads to generation of the measurement request signal (CCR) and its transmission to the sensor array. This in turn causes the processor, and thus the EMU, to receive a first set of battery parameters from the sensor arrayduring a charging event or mode of the battery. Additionally, the processoris also caused to receive a second set of battery parameters from the sensor arrayduring a discharging mode of the battery. The first and second sets of battery parameters are communicated as part of the input signals (CC) and include at least a voltage, a current, and a temperature of the battery.

Once the battery parameters have been communicated and received, the processorcalculates the charge-side resistance (R) of the batteryduring the charging mode. This occurs using the first set of battery parameters. The processoralso calculates the discharge-side resistance (R) of the batteryduring the discharging mode, which occurs using the second set of battery parameters. Thereafter, the processoris caused to calculate aging or a degradation level of the batteryusing the charge-side resistance (R) and the discharge-side resistance (R), and to thereafter perform a protective action in response to the degradation level exceeding a calibrated threshold.

An exemplary embodiment of the methodis illustrated in. Commencing with block B(“SOC, T”), the EMUdetermines the SOC and temperature of the battery. SOC may be determined via the SOC blockof, e.g., using Coulomb counting, machine learning, voltage and temperature-based lookup tables, OCV-SOC curves, or other possible approaches as noted above. The temperature measurement blockdescribed above with reference tomay be used to ascertain the temperature of the battery. The methodproceeds to block Bafter recording the SOC and corresponding temperature in non-volatile components of the memory.

Block B(“IDD-1”) entails measuring the battery current via the current sensor (S) of. As with block B, the measured value is recorded in non-volatile components of the memory. The methodthen proceeds to block B.

At block B(“Charge/Discharge?”), the EMUdetermines whether the batteryis in a charging mode or a discharging mode. For instance, the EMUmay determine the current flow direction of the measured current from block Band other information, such as the state of the charging switchof, to determine that the batteryis actively charging or discharging. The methodthereafter proceeds to block Bwhen the EMUdetermines that the batteryis in the charging mode, and to block Bin the alternative when the EMUdetermines that the batteryis in the discharging mode.

At block B(“Obtain OCV@ SOC”) of, the methodnext determines the open circuit voltage (OCV) during the charging mode for the present SOC from block B, i.e., SOC. As illustrated in the plotof, OCV is specific to a given SOC. As appreciated in the art, OCV also increases with decreasing temperature (and vice versa). Therefore, block Bis determined at the temperature measurement taken at block B. The methodthereafter proceeds to block B.

Block B(“Obtain OCV@ SOC”) is analogous to block B, but is performed during a charging mode of the battery. Block Bincludes determining the open circuit voltage (OCV) during the charging mode for the present SOC from block B. As illustrated in the plotof, OCV is specific to a given SOC. As appreciated in the art, OCV also increases with decreasing temperature (and vice versa). Therefore, block Bis determined at the temperature measurement taken at block B. The methodthereafter proceeds to block B.

Blocks Band B(“V2” and “V1”, respectively) include measuring the voltage of the batteryvia the voltage sensor (S) of. This value is then recorded in non-volatile components of the memory. The methodthereafter proceeds to block B(from block B) or B(from block B).

Block B(“R2 @ SOC”) is performed during a discharging mode of the batteryto calculate the discharge-side resistance (R). As with block Bdescribed below, the methodproceeds to block Bonce the discharge-side resistance (R) has been determined and recorded in non-volatile memory.

At block B(“R1 @ SOC”), the EMUnext calculates the charge-side resistance (R) at the current SOC from block B, i.e., the temperature-specific value SOC. Using ohmic resistance for simplicity, R1 may be set equal to v1/I, with V1 being the voltage measured in block Band/being the current IDD-1 measured in block B. The methodproceeds to block Bonce the charge-side resistance (R) has been determined and recorded in non-volatile memory.

Still referring to, block B(“Health Check”) includes performing a health check of the batteryvia the EMUusing the recorded values of the charge-side resistance (R) and discharge-side resistance (R) from respective blocks Band Bas described above. Block Bmay be implemented in various ways depending on the application. For instance, the instructions embodying the methodmay be executable by the processorofto cause the EMUto calculate a degradation level of the batteryor a comparable state of health (SOH) as a function of the resistances Rand R.

One possible approach is to evaluate the absolute difference between the charge-side resistance (R) and the discharge-side resistance (R). As noted above, these values are equal when the batteryis new, i.e., R=Ras shown in. As shown in, however, an aging/degrading batterywill experience an ever-increasing internal resistance disparity as the charge-side resistance (R) increases faster than the discharge-side resistance (R). Therefore, a possible strategy implementable by the EMUis to compare the charge-side resistance (R) to the discharge-side resistance (R) to ascertain the magnitude of the difference. This magnitude of difference may be used as the degradation level.

Alternatively, the EMUmay track the values of the charge-side resistance (R) and the discharge-side resistance (R) over time, calculate the rate of change of each, and then compare the rates of change to each other to determine a difference or delta therebetween. In this instance, the instructions embodying methodare executable by the processorto cause the EMUto calculate a ratio of (i) a rate of increase of the charge-side resistance to (ii) a rate of increase of the discharge-side resistance. This calculated ratio may be used in one or more embodiments as the degradation level. The methodproceeds to block Bwhen the EMUhas determined the degradation level of the battery.

At block B(“Battery SOH=OK?”), the EMUnext determines, using the above-described degradation level, whether the present operating state of the batteryis sufficiently healthy to continue its use without intervention. For example, a lookup table may be populated with escalating multiples of the discharge-side resistance (R) or a value based thereon, with the EMUcomparing the charge-side resistance (R) or values based thereon to the threshold(s).

Using a simplified example of this in which the degradation level is a magnitude of an absolute difference between Rand R, i.e., |R−R|, a lookup table in memoryof the EMUcould be populated with thresholds of, for example, 1.5R2, 2R2, 3R2, 4R2, etc. When using the rate of change of the charge-side resistance (R) and the discharge-side resistance (R), similar graduated thresholds may be employed, for instance

etc. The methodproceeds to block Bwhen the EMUdetermines that the degradation level satisfies one of the programmed threshold conditions, i.e., that the batteryhas aged or otherwise degraded to the point that invention is required. The methodreturns in the alternative to block Bwhen the EMUdetermines that the batteryhas not aged or deteriorated in a meaningful way.